Power supply circuits can be implemented in a variety of computer and/or wireless devices to provide power to circuit components therein. One example of a power supply system is a discontinuous flyback power regulator, in which current flow through a primary winding of a transformer induces current flow in a secondary winding of the transformer, such that an output voltage can be generated based on the current flow in the secondary winding. As a result of this configuration, the primary-side circuit components can be isolated from the secondary-side circuit components. To accurately regulate the operation of the discontinuous flyback power regulator, it may be necessary to determine the output voltage to maintain the output voltage at a given magnitude. However, to maintain isolation between the secondary-side circuit components and the primary-side circuit components, the output voltage can be measured based on a voltage in the windings of the transformer.